Patent GB-905062-A (GB)
Title: Improvements in or relating to hydraulic actuator systems
Inventor: CAMERON-JOHNSON ALAN
IPC: B64C13/24
Filed: 1959-06-29
Abstract: 905,062. Hydraulic apparatus. DOWTY ROTOL Ltd. June 16, 1960 [June 29, 1959], No. 22291/59. Class 69 (2). [Also in Group XXXI] An hydraulic actuator system comprises a master actuator 11, Fig. 1, movement of which causes related movement of a slave actuator 11<SP>1</SP>, and means for biasing the actuators towards predetermined intermediate and related positions. The master actuator, which may be of similar construction to the slave actuator, consists of a cylinder having bores 14, 15, bore 15 receiving a piston 21 having a rod 22 which, in one direction extends from the cylinder and is attached to a control member 25, and in the other direction extends through a partition 16 into the bore 14. A biasing piston 34 is disposed in the bore 14 and has a rod 35 extending into the hollow end of the rod 22 and formed with a flange 37. The bore 14 is connected by a line 43 to the bore 14<SP>1</SP> of the slave actuator, and the bore 15 is connected by lines 41, 42 to the bore 15<SP>1</SP> of the slave actuator. A source of fluid pressure is connected by a line 44, combined reducing and relief valve 45, and line 46 to the line 43 and the bores 14, 14<SP>1</SP> to act on the biasing pistons 34, 34<SP>1</SP>, which are urged to the left to a position engaging the ends of the bores, and to act on the ends 33, 33<SP>1</SP> of the rods 22, 22<SP>1</SP> which are moved to a central position, wherein the flanges 37, 37<SP>1</SP> engage the ends of the rods. Movement of the control member 25 to move the piston 21 in one direction or the other causes a corresponding movement of the piston 211 and rod 221 of the slave actuator. When the member 25 is released, the fluid pressure in the bores 14, 14<SP>1</SP> returns the pistons 21, 21<SP>1</SP> to their central position. The line 43 leading from the source of fluid pressure is connected by a line 47 and oneway valves 49, 50 to the bore 15 whereby leakage of fluid from the system is replenished. Relief valves 54, 55 are provided to pass fluid to an exhaust line 51 in the event of excessive pressure resulting from a rise in temperature. In another embodiment, the fluid pressure supplied to the bores 14, 14<SP>1</SP> to bias the actuators to their central positions can be disconnected when the control member is operated to move the actuators, a valve between the reducing valve 45 and the bores 14, 14<SP>1</SP> and one-way valves, which may be disposed within the piston and connected to the valve 45 by bores in the rod of the piston, being operated by a cam movable by a manually-operable plunger on the member 25. In a further embodiment for operating the nose wheel of an aircraft, a rudder 210, Fig. 3, transmits movement through a device 211 and differential unit 212 to a steering selector 214 controlling the displacement of an actuator 215 connected by a linkage 217 to the wheel of the aircraft and a master actuator 218, in turn connected to a slave actuator 219. The actuators 215, 219 have centring devices 216, 222 supplied with fluid pressure from a line 230. Pressure-relief valves 224, 225 are connected to an exhaust line 229 to prevent excess pressure in the actuators, and one-way valves 226, 227 are connected to a supply line 228 to replenish leakage of fluid.